This invention relates to a lock mechanism and in some aspects to a dual function lock mechanism. In another aspect, the invention relates to a privacy lock assembly.
It is common practice to fit doors with separate latch bolt and deadlock fittings. The latch bolt is typically handle actuated, while the deadbolt is usually associated with a conventional double-cylinder deadlock for key release or engagement from either side of the door.
It is also known to provide deadlock mechanisms in which the deadbolt has an angled rather than rectangular tip, and may be projected to an extended lock position when a contact pin or auxiliary bolt is retracted by engagement with the strike plate of the door jamb. Such a mechanism is shown, for example, in Australian patent 540386. A commonly used form of this type of mechanism provides for the bolt to be key locked in the extended position from the inside of the door. These mechanisms are generally mounted on a housing on the inside face of the door and are not readily adaptable for use with high quality door knobs. They also have the disadvantage that, when a person uses the key to open the door from the outside, the inside key cylinder must be separately unlocked or the door will remain totally deadlocked when it is shut behind the entering person. This is not necessarily desirable from a safety point-of-view.
Various combination latch and deadbolt mortice lock mechanisms are known but these require the provision of a very substantial rectangular cavity in the body of the door.